Fuse indicator



F. Q. LA EMM?! FUSE INDICATOR Filed Aug. 25, 1935 Patented Dec. l, 1936UNITED STATES PATENT OFFICE 3 Claims.

This invention relates to electrical fuses, especially toelectricalfuses of the cartridge type, and more particularly to anindicator for such fuses which acts to give information as to theintegrity of the fusible element.

Itis well understood by those skilled in the electrical art that safetyrequires all circuits which carry or are capable of carrying anappreciable amount of current must have safety devices inserted in themto prevent an excessive flow of current under abnormal conditions.

A common safety device ls the well known fuse made of a strip of metalwhich will melt upon the now therethrough of an undesirable heavycurrent.

Fuses are made of many forms amongst which is the cartridge fuse whichmay be either of the ferrule type or the knife blade type.

In either case it is convenient and desirable to have means of simpleform by which the fact that the fusible metal has melted may beindicated without removing the fuse from its position and disassemblingit.

Integrity indicator means have been devised for application to both theferrule type and the knife blade type of fuse, but these indicators areof a form which does not insure a positive and unfailing retention inposition upon the fuse where extreme vibration occurs.

A principal object of applicants invention is the provision of anindicator applicable particularly to fuses of the knife blade type bywhich the integrity of the fusible element of the fuse may beascertained by a visual inspection without disassembling the fuse ordisturbing the position thereof, and which will be of such a form thatno Vibration, however extreme, will cause the indicator to becomeseparated from the fuse.

Other objects and advantages will appear as the description of theparticular physical embodiment selected to illustrate the inventionprogresses, and the novel features of the invention will be particularlypointed out in the appended claims. l

In describing the invention in detail and the particular physicalembodiment selected to illustrate the invention, reference will be hadto the accompanying drawing, and the several views thereof, wherein likecharacters of reference designate corresponding parts throughout theseveral views, and in which:

Figure 1 is a side elevational view of a conventional knife bladecartridge fuse in place in the usualand conventional clips with anindicator embodying applicants invention shown therewith; Fig. 2 is across-sectional view of the device as shown by Fig. 1 on the planeindicated by the line II-II of Fig. l, viewed in the direction of thearrows at the ends of the line; Fig. 3 is a perspective view ofapplicants indicator.

Numeral I designates an ordinary and conventional mounting panel uponwhich are the ordinary and well known binding bolts 2 and 3, forattaching the conducting wires 4 and 5 of a circuit in which a fuse isto be inserted. Bolts 2 and 3 10 are connected by means of metallicstrips 6 and 'I to the usual fuse clips' 8 and 9.

A usual and conventional form of knife blade cartridge fuse ID, havingblades II and I2, and metallic caps I3 and I 4, and metallic ferrules I515 and I6, is positioned connecting the clips 8 and 8.

In order to visually indicate the integrity of the thermal element ofthe fuse I0, applicant provides an indicator which embodies a lamp I'I.This lamp Il, in accordance with applicants invention, is connectedbetween the knife blades II and l2. When the thermal element of a fuseIll is intact the lamp exhibits no glow but when the thermal element ofthe fuse Ill has been destroyed the lamp l1 becomes illuminated.

Applicant `provides a metallic arm I8 formed with a slot I9. This slotI9, as best shown in Fig. 2, is adapted to embrace a blade of the fuse.1t is also of a thickness such that it may well be positioned between acap as I3 and a clip as 8. 30 When the arm I3 is in the position asshown by Fig. 1, it is impossible to remove the arm from the fusewithout rst removing the fuse from the clip.

For making electrical connection to the other 35 fuse blade applicantprefers a metallic spring clasp 2l, best shown in Fig. 3; This metallicspring clasp may be readily pushed on to the cap I4 or removedtherefrom.

Between the arm i8 and the spring clasp 2| 40 applicant preferablyprovdesra supporting covering and protecting insulating tube 22. Thistube is connected at one end to the arm I8 and at the other end to the'spring clasp 2l in any suitable and appropriate manner. Applicant 45prefers to employ metallic bushings 23 and prefers to rigidly attach thebushings to the tube 22 by means of rivets as 24 and to then rivet as byrivets 25 the arm I8 and the spring clasp 2| to the bushings 23.

The lamp Il is preferably of the glow type having two electrodestherein, 2G and 33, and having two terminals 21 and 28. One of theterminals 21 is electrically connected to the arm I 8. The otherterminal 28 is connected to a 55 leak resistance 29 and by means of aconductor 30 to the spring clasp 2|.

The connection of terminal 21 to arm i8 and conductor 30 to spring clasp2| is preferably effectuated by means of eyelets, as li, which passthrough the arm and spring clasp and are upset at each end. After theeyelets 3| are upset, the terminal 21 and the conductor 30 are securelyheld in place by a drop of solder as 32,

From the above description it will be readily seen that the indicator ofapplicants invention is of a form such that it may be placed in positionupon a knife blade cartridge fuse with great facility before thatcartridge fuse is placed in clips, but after the cartridge fuse isplaced in clips it is impossible to remove the indicator, so thatvibration, no matter how severe, would not cause the indicator to becomeseparated from the fuse.

Although I have particularly described one particular physicalembodiment of my invention, and the principle and construction thereof',nevertheless, I desire to have it understood that the form selected ismerely illustrative but does not exhaust the possible physicalembodiments of the idea of means underlying my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In an integrity device for a cartridge fuse, in combination: ametallic arm formed with' a slot adapted to receive a fuse blade and bepositioned between a cap of a fuse and a fuse clip whereby the armcannot be removed except when the fuse blade is out of the clip; anelectrical indicator having two terminals, one of the terminalselectrically connected to the said arm: and means for electricallyconnecting the other terminal to the other fuse blade.

2. In an indicator, for a cartridge fuse of the type having a blade oneach end and a cap surrounding the blade adapted to be held in fuseclips, in combination: a metallic arm formed with a slot adapted toreceive a fuse blade and be positioned between a cap and a clip wherebythe arm cannot be removed from the blade without first removing the fuseblade from the clip; an electrical indicator having two terminals; meansfor electrically connecting one of the terminals to the arm; a metallicspring clasp adapted to embrace the cap on the end of the fuse remotefrom the arm; and means for electrically connecting the other terminalof the indicator to the metallic clasp.

3. In an indicator for a cartridge fuse, in combination: a metallic armformed with a slot adapted to receive a fuse blade and be positionedbetween a cap ofi-a fuse and a fuse clip whereby the arm cannot beremoved from the blade without first removing the fuse blade from theclip; an indicator lamp forming electrical connection with the arm andsupported thereby; and means also connecting the lamp electrically withthe other blade of the fuse.

FRANK C. LA MAR.

